Integrated Circuit Implementation for a GaN HFET Driver Circuit

This paper presents the design and implementation of a new integrated circuit (IC) that is suitable for driving the new generation of high-frequency GaN HFETs. The circuit, based upon a resonant switching transition technique, is first briefly described and then discussed in detail, focusing on the design process practical considerations. A new level-shifter topology, used to generate the zero and negative gate-source voltages required to switch the GaN HFET, is introduced and analyzed. The experimental measurements included in this paper report the results of tests carried out on an IC designed and fabricated as part of the multiproject die in high-voltage process H35B4 of Austriamicrosystems. They fully demonstrate the performance of the proposed driver that opens the possibility of fully exploiting the wide capabilities and advantages of GaN devices for use in power electronics applications

Optimum switch sizing for class DE amplifier

Recently, integrated class DE ampli fiers without matching networks have been proposed as a compact solution to drive a multi-element piezoelectric ultrasound transducer array for high-intensity focused ultrasound (HIFU) therapy. These transducers produce acoustic energy that translates into heat for tissue ablation. In order to steer the focal zone, each element in the transducer array is driven at a different phase. Hence, there's a need for the power amplifi er with a digital control unit in this application. Since each element in the transducer array has a different electrical characteristic and they have to be driven at the same frequency, it is a challenge to drive all transducers in the array at their optimum conditions. This work introduces strategies to determine efficient driving parameters for an entire transducer array. In addition. a method to improve the power efficiency of the class DE amplifi er by choosing the optimum size for switching MOSFETs is also proposed. During the operation of a class DE ampli fier, losses are caused by the ON resistance and the drivers of the MOSFET gate capacitances. These parameters are directly dependent on the size of the switching MOSFETs. A wider MOSFET will have a higher gate capacitance, but lower ON resistance. With the correct sizing, these losses can be greatly reduced to improve power efficiency and prevent excessive heating. The challenge with this method is the wide selection of transducers with varying impedance. As the load impedance changes, the MOSFET size also needs to be changed to maintain the maximum power efficiency. Also, the proposed design must deliver at least 1 W output power to the transducer in order to produce enough acoustic pressure. This output requirement will limit the available technology that can be used to design the amplifi er. In addition, this work also proposes a new driving circuit that consumes less power to operate, and also allows a full 0-360 degree phase shift. The design is simulated with Spectre simulator using 0.35 m 50V CMOS process data available from Austria Micro Systems. The proposed design can deliver 1422mW of average power to 6-elements transducer array, and achieve up to 91% power efficiency